login shell

The goal here is to separate the users having a login shell from the others:

1
2
3
4
5
6
7
cat -n inputfile | sed -En -e '
  \=(/usr/sbin/nologin|/bin/false)$= { H;d; }
              # Append matching lines to the hold buffer
              # and continue to next cycle
  p           # Print other lines
  $ { g;p }   # On the last line,
              # get and print the content of the hold buffer

What is a login shell ?